Guys when i get to max lvl(whatever that is?)in Borderlands in single player then go co-op will i still be able to use my max lvl character? Or do you have to start a fresh character for co-op?

You can do either. The thing is if you use your max level character and join with someone who is just starting a new game, or they join your game, you will have to protect them until they level up a lot.

The game is tougher in co-op and it seems to try to split the difference between your level and other players. Best is to start a new game together. Max level is insanely powerful btw.